#include<fstream.h>
#include<math.h>
long n,m,s=1,c,d=2000000,aux,z=0,j;
int main()
{
ifstream f("fact.in");
ofstream g("fact.out");
f>>n;
if(n==0) g<<"1";
else
{
m=(d+s)/2;
while (z!=n&&s!=d)
 {j=1;c=5;z=0;
  while (c<=m)
   { aux=m/c;
    j++;z+=aux;
    c=pow(5,j);
   }
  if(z>n) {d=m-1;m=(d+s)/2;}

  else if(z<n) {s=m+1; m=(d+s)/2;}
  }
if(z==n) {m=m-m%5;
	  g<<m;   }
 else g<<"-1";
}
f.close();
g.close();
return 0;
}